Energetic and propellant materials, including perchlorate, explosive components, and their breakdown products are contaminants of concern to the Department of Defense (DoD). The emergent contaminants perchlorate, 1,4-dioxane, and N-nitrosodimethylamine are highly soluble, potentially hazardous and recalcitrant propellant and energetic contaminants. The important properties of perchlorate salts (ammonium, potassium, magnesium, and sodium) include:
solubility of its salts in aqueous solution and organic solvents
stability in aqueous solution
non-volatility.
These physicochemical properties contribute to the large perchlorate plumes in aquifers that supply drinking water.
Perchlorate has contaminated surface and groundwater resources at various locations in the United States. Most of the perchlorate manufactured in the United States is used as the primary ingredient of solid rocket fuel for military missiles and the space shuttle, although it has also been used in fireworks, safety flared, matches and car air bags. Manufacturing, testing, and training operations have released perchlorate into the environment where it has contaminated soil, groundwater, and surface water. Wastes from the manufacture and improper disposal of perchlorate-containing chemicals are increasingly being discovered in soil and water.
Perchlorate is both a naturally occurring and man-made chemical that impacts human health by interfering with the functioning of the thyroid gland. The thyroid regulates metabolism in adults and proper development in children. Thyroid gland tumors have been linked to perchlorate exposure. As a potential endocrine disrupter, perchlorate can threaten the health of both human and wildlife populations.
NDMA, a probable human carcinogen, is produced by the oxidation of 1,1-dimethylhydrazine (UDMH) which is mainly used in rocket fuel production. NDMA is a yellow oily liquid that is semi-volatile, very soluble in water and highly mobile in soil. Due to the physical and chemical properties of NDMA, conventional physical and chemical treatment processes have been either expensive or ineffective. Both perchlorate and NDMA have been identified as co-contaminants in DoD wastewater.
1,4-Dioxane is used as a stabilizer of solvents such as 1,1,1-trichloroethane, and often remains as a residual contaminant following remediation of the highly volatile solvent. 1,4-dioxane is more soluble than the compounds with which it is released, resulting in rapidly expanding groundwater plumes.
There is currently a lack of sustainable cost-effective remediation technologies to address the widespread perchlorate contamination of water resources. The cost of treating perchlorate and other emergent contaminants in water using existing technologies (ion exchange and granular activated carbon) is a growing financial burden. This is because perchlorate is a highly soluble anion with poor affinity for most sorbents used in conventional water treatment. The relative adsorption of perchlorate to other anions in water is given by: HCrO4−>Cr42−>ClO4−>SeO42−>SO42−>NO3−>Br−>(HPO42−, HAsO42−, SeO32−, CO32−)>C−>NO2−>Cl−>(H2PO4−, H2AsO4−, HCO3−)>OH−>CH3COO−>F−.
Additionally, although ion exchange is a reliable, proven technology for perchlorate removal from water sources, treatment and disposal of the resulting concentrate is the limiting factor in successfully applying this technology at some water utilities. Treatment of perchlorate-contaminated water using ion exchange processes, reverse osmosis, and nanofiltration all generate a large volume of perchlorate-rich waste brines that may be difficult to dispose. Further treatment of the brine is needed to reduce its volume or toxicity before disposal. Initial studies in this area have identified biological degradation as a promising technique to accomplish this goal. However, reuse of treated ion exchange brine has an adverse impact on distribution system water quality. Microorganisms used for perchlorate/nitrate destruction in the concentrate could possibly grow on ion exchange resins, with potential of getting into the effluent and distribution system. The American Water Works Research Foundation (AWWAR) and the United States Environmental protection Agency (EPA) have been seeking low-cost sustainable technologies for treatment of perchlorate-rich waste brines.
Granular activated carbon (GAC) is not a good sorbent for the highly soluble solutes, i.e. emergent contaminants. Tailored GAC may be good sorbents but are more expensive than the low-cost tailored clays, due to capital cost and treatment of the regenerant.
The cost of treating perchlorate and other emergent contaminants in water using existing technologies (ion exchange and granular activated carbon) is a growing financial burden.
These and other problems exist. Previous attempts to solve these and other problems include the following.
In many municipal water districts, Amberlite PWA2 resin and other ion selective resins are used to manage perchlorate contamination concerns. Specific approaches include:                Resins—regenerable and non-regenerable selective ion exchange resins        GAC and tailored GAC        Nanofiltration materials        Chemical destruction of the contaminants (compounds)        Biological degradation of the contaminants in fluidized bed and packed bed reactors, and injection of electron sources into the contaminated water to enhance biodegradation of perchlorate.        
U.S. Pat. No. 4,740,488, issued to Fogler et al. on Apr. 26, 1988, discloses a modified clay that is a general purpose sorbent for the removal of trace organic pollutants from process effluent streams. An expandable smectite clay, such as montmorillonite, is placed in an aqueous suspension to expand the layers. The expanded clay is then treated with an excess of a solution of hydroxy-aluminum, in particular, a hydroxy-aluminum solution having an OH−/Al ratio of about 2.54 and a pH in the vicinity of 4.5. The weight of clay to volume of hydroxy-aluminum solution may vary from about 1:10 and 1:25. The treated clay is filtered, washed, dried, and powdered, and then the entire treatment sequence is repeated. The modified, powdered clay removes organic pollutants from industrial effluent in the ppb-ppt range. In particular, the modified clay is useful in removing traces of PCBs and Dioxin.
U.S. Pat. No. 4,916,095, issued to Fogler et al. on Apr. 10, 1990, discloses a modified clay sorbent and method of treating industrial effluents to remove trace pollutants, such as dioxins, biphenyls, and polyaromatics such as benzo(a)pyrene and pentachlorophenol. The clay sorbent has a composite structure in which the interlayer space of an expandable clay, such as smectite, is filled with polyvalent or multivalent inorganic cations which forces weaker surfactant cations to locate on the surface of the clay in such an orientation that the resulting composite is hydrophobic in nature. In certain embodiments, a non-expanding clay, such as kaolinite, is used and surfactant cations are necessarily located on an external surface of the clay.
While these patents and other previous methods have attempted to solve the above mentioned problems, none have utilized or disclosed cost-effective, tailored, earth materials that filter perchlorate and emergent contaminants from freshwater and brines and that are degraded using bioremediation processes, as does the present invention.
Therefore, a need exists for tailored earth materials with these attributes and functionalities. The tailored earth materials according to the present invention substantially depart from the conventional concepts and designs of the prior art. It can be appreciated that there exists a continuing need for new and improved tailored earth materials which can be used commercially. In this regard, the present invention substantially fulfills these objectives.
The foregoing patent and other information reflect the state of the art of which the inventor is aware and are tendered with a view toward discharging the inventor's acknowledged duty of candor in disclosing information that may be pertinent to the patentability of the present invention. It is respectfully stipulated, however, that the foregoing patent and other information do not teach or render obvious, singly or when considered in combination, the inventor's claimed invention.